Channel selection filters are commonly applied in wireless communication receivers. One purpose of the application of a channel selection filter (CSF) is to achieve a final analog filtering before analog-to-digital conversion (ADC), to suppress any unwanted components of the received signal (e.g. adjacent channel interference) that remain after the previous processing by the receiver front end.
A CSF is often realized as an Infinite Impulse Response (IIR) filter, typically a Chebyshev filter of a certain filter order. A high filter order may typically achieve better suppression of undesired signal components outside of the pass band of the filter than a low filter order. However, a high filter order typically also increases cost, complexity and/or power consumption of the filter.
An example group of scenarios where the CSF implementation may be of particular importance is when an interference signal (also referred to herein as a blocker, an unwanted signal, an undesired signal, etc.) is present close to the frequency band of the desired signal, which frequency band typically corresponds to the pass band of the CSF. To be able to sufficiently suppress this type of interference signal it may be necessary to apply a CSF of high filter order.
In some of these scenarios, such an interference signal may not be continuously present, but may appear and disappear depending on various conditions (e.g. radio environment). Thus, to reduce the power consumption, two (sets of) channel selection filters may be used, one with high filter order to be applied when the interference signal is present (or otherwise in radio conditions that require high suppression outside the pass band) and one with low filter order to be applied otherwise (e.g. when the interference signal is not present). The channel selection filter with low filter order may be seen as a default channel selection filter.
However, since the digital processing of the received signal is typically designed for a particular CSF design, a problem will occur when switching between two different CSF designs is applied. Particularly, data may be corrupted during and/or after the switch.
Therefore, there is a need for methods and arrangements of wireless communication receivers that enable use of two (or more) different channel selection filters, and switching there between, while avoiding (or at least reducing) negative impact on the overall performance of the receiver.